Refilling a Combi Boiler.

Sounds rather like you took the pressure gauge past the red line.

fire up and run for an hour, bleed any rads that need bleeding and don't forget to add inhibitor asap

treacleminer12 wrote in news: snipped-for-privacy@diybanter.com:

If you drained the system through the safety valve the the most likely cause woud be there is some crapunder the seating or the the valve has not reseated after twisting it to drain.

Twist the knob several times so that it goes clunk clunk a few times. Also open the filling loop whilst doing this, this could help to blow any crap from the seating.

If this does not stop the leak then you would likely need a new safety valve.

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I'm running at ~1 bar, would 2 or 2.5 help in any way?

I don't know because I don't know which boiler you've got, but mine needs to be between 1 and 3 bars, and the manual says the optimum is 2. Most condensing boilers operate best at 2 bars

Mine says 1-1.5 in the instructions (cold), depending on the total volume of the system.

I set mine to 1 bar at 20C. It goes up to 2 bar when running. The boiler can operate down to 0.25 bar in theory because it could also be used in a vented system.

There's also a layout factor - a minimum of 0.1 bar for every metre the pressure guage is below the highest point in the sealed system plumbing, plus a fudge factor, or you won't be able to force water to the top of the system to get the air out. This is only likely to be an issue in a 3 or 4 storey house with the guage in the basement.

Operating the system at higher pressure than is necessary will stress some parts a little more. It might shorten the life of some seals, such as shaft seals on valves.